A driver for a BLDC motor usually includes a voltage decreasing unit for decreasing AC mains voltage, a rectifier for rectifying the decreased AC voltage to a DC voltage, and an inverter which is powered by the DC voltage and commutates the power supplied to the BLDC motor. In prior art drivers, the speed of the motor can be adjusted by changing the PWM signal provided to the inverter.
The present invention aims to provide a new power supply circuit which is particularly suitable for a variable speed electric motor powered by an AC mains power supply.